Studies in the biochemistry of cirripede eggs. VI. Changes in the general biochemical composition during development of Tetraclita squamosa rufotincta Pilsbry,Balanus perforatus Brug., and Pollicipes cornucopia Darwin

The carbohydrate, protein, lipid, total RNA and DNA at four stages in the development of the eggs of Tetraclita squamosa rufotincta Pilsbry, Balanus perforatus Brug., and Pollicipes cornucopia Darwin have been determined. The initial caloric content varies with species, that of the large egg of Tetraclita being extremely high; on a relative volume-specific basis, however, differences, although still present, are much less variable. A comparison has been made with other species. Those eggs in which lipid predominates over protein in Stage I lose more lipid during development. The relatively large quantities of reserves in Tetraclita may serve as metabolic substrate during the development of the planktonic larvae under nutrient-poor conditions.     

The lipid,fatty acid and amino acid composition of ratite eggs from three different species of kiwis Apteryx australis mantelli,A. haasti and A. oweni bred in captivity on the same diet

The lipid composition of the eggs obtained from three different species of New Zealand kiwis (Apteryx australis mantelli, A. haasti and A. oweni) were investigated and compared. Although those of A. australis mantelli were known to have high levels of triacylglycerols and Iow levels of phospholipids (83% and 8% respectively), the other species had reduced quantities of triacylglycerols (65–69%) but compensated with increased levels of phospholipids (23–24%). These findings were similar to those of the domestic hen eggs. As regards to the proportion of lipid to protein in the kiwi eggs, A. australis mantelli and A. haasti contained similar ratios of 1.00–0.51 but A. owenihad higher levels of lipids, 1.00–0.38. The distribution of amino acids in each case was similar.     

Assessment of biochemical composition and energy reserves in larvae of the scallop Patinopecten yessoensis

Larvae of Patinopecten yessoensis increased in dry weight from ≈ 150 to 1000 ng per larva during the larval development period of 28 days. Microanalytical procedures were developed to determine the lipid, protein, carbohydrate, and ash contents from which energy levels and condition indices were derived. Replicate analyses of two sizes of P. yessoensis larvae gave coefficients of variation at or <5% for the biochemical analyses. Lipid and protein were identified as major components, and carbohydrate as a minor component providing 56.6,37.6, and 5.8 %, respectively, of the calculated energy content. The energy content of the eggs of P. yessoensis was 2.4 and 3.1 times higher than the larvae of P. yessoensis and Crassostrea gigas, respectively, derived from 20.6% lipid, 54.6% protein, and 7.2% carbohydrate. The carbohydrate in the eggs was stored principally as a glucan, considered to be glycogen, which was absent in the developing larvae. Changes in biochemical composition of P. yessoensis larvae during development showed that lipid and protein reserves were lost for ≈ 20 days and then lipid accumulated as the larvae reached premetamorphic condition.     

Organic,inorganic, and caloric composition of eggs,pentaculae, and adults of the brooding sea cucumber Cucumaria curata cowles (Echinodermata: Holothuroidea)

Levels (percentage composition) of water, ash, carbohydrate, lipid, protein, and calories were determined for eggs, pentaculae, and adults of the sea cucumber Cucumaria curata Cowles. Component contents (μg/individual) were calculated for eggs and pentaculae. During the 28 days of development to hatching, the large yolky eggs gain water and ash, the total dry weight increasing from 169 to 190 μg/egg during embryogenesis. There were no statistically significant changes in lipid, protein, and caloric contents during embryogenesis, but carbohydrate decreased by 0.82 μg/egg.The decrease in carbohydrate is sufficient to account for estimated embryonic energy requirements. Based on the utilization of carbohydrate, embryos of C. curata show a nutritional pattern similar to that of the planktonic embryos of sea urchins and different from that of embryos developing from terrestrial eggs, freshwater eggs, and planktonic and demersal marine eggs.Although broods varied widely in egg number and mean egg dry weight, C. curata gives eggs which contain a constant proportion of organic components.Levels of ash, water, and protein in the adults exceeded those in the pentacula, and lipid comprises a much smaller proportion of the adult body than it did of the pentacula.     

Biochemical changes during embryonic development in the aquatic hemipteran bug Laccotrephes griseus

Protein, carbohydrate, free amino acid, lipid, RNA levels, and electrophoretic changes in the protein profile were determined in the eggs of the water scorpion, Laccotrephes griseus, during normal embryonic development. The protein levels remain lower and relatively constant in the eggs of 0, 1 and 2 days of age, while in the eggs of older groups, i.e. between 2 and 6 days, a marked increase in the protein level occurs. Then its level declines. The RNA content shows a rise up to the day 6 stage, later it declines sharply, indicating an increase in the degree of synthetic activity that takes place during such period of embryonic development. Electrophoretic and densitometric analysis show the qualitative and quantitative changes of yolk protein reflecting the utilization of already existing proteins as well as the appearance of new proteins.Water content increases gradually as development proceeds. There is a steady depletion of carbohydrate and lipid during the course of embryonic development. The nature of yolk components as well as their preferential utilization during embryogenesis has been discussed in relation to the generally accepted view that protein serves as the source for the embryonic metabolism in aquatic insects does not hold good for L. griseus and other freshwater insects.     

Energy metabolism in developing Ascaris lumbricoides eggs. I. The glycolytic enzymes.

The changes in the activities of the glycolytic enzymes were followed during the development of Ascaris lumbricoides eggs. The maximum catalytic capacities of the major catabolic pathways were estimated from the maximum activities of the nonequilibrium enzymes, and the results are compared with the changes in metabolic rate and the changes in carbohydrate and lipid utilization which occur during development. Although the onset of carbohydrate and lipid utilization was accompanied by an increase in the catalytic capacities of the corresponding pathways, there was no drop in the catalytic capacities of the pathways when the eggs became dormant, nor was there any change when the dormant egg was activited.     

The chemistry of egg maturation in the unfed mosquito Aedes atropalpus

The mosquito Aedes atropalpus, maintained without a blood meal and without sugar, matures 150 to 200 eggs. The gradual accumulation of protein and triglyceride in the maturing eggs could be entirely accounted for by the gradual disappearance of protein and lipid from the abdomen (fat body).     

Nutrient Composition of Romanomermis culicivorax in Relation to Egg Production and Metabolism

The nutrient composition of postparasitic females (newly emerged juveniles, newly molted adults, and spent adults) and eggs of Romanomermis culicivorax was studied. Throughout post-parasitic development, proteins increased and lipids decreased progressively as a proportion of the dry weight; the proportion of glycogen within the nematodes remained stable. The greatest decrease in the lipid moiety occurred during egg production. Eggs contained relatively low levels of lipids (12% dry weight), and ca. 20% of the dry weight of the eggs was unaccounted for by lipid, protein, and glycogen determinations. Chitin, mucoproteins, and peptides were present in the eggs. The fatty acid composition of nematodes remained constant during postparasitic development; eggs contained a similar profile of fatty acids as postparasites, with marginally higher content of unsaturated fatty acids. Radiotracer studies showed that the eggs could oxidize glucose and palmitic acid.     

Immunological studies of insect metamorphosis. II. The role of a sex-limited blood protein in egg formation by the Cecropia silkworm

1. In the pupal stage of the cecropia silkworm, antigen 7, a protein with the solubility characteristics of an albumin, is present in female blood in approximately a thousand times higher concentration than in the blood of males. Antigen 7 is undetectable in the blood of larvae of either sex. It first appears in the blood after the larva has spun its cocoon, and is present throughout all subsequent stages of metamorphosis. Late in the pupal-adult transformation, when the eggs are produced, the concentration of antigen 7 in female blood decreases significantly. 2. An antigen which could not be distinguished from antigen 7 immunologically is present in solution in the yolk of unfertilized eggs. 3. In females which, by ovariectomy, were prevented from forming eggs, the concentration of antigen 7 in the blood increased during the usual period of egg formation rather than undergoing the normal decrease. Ovaries transferred to the hemocoel of males produced eggs but were unable to incorporate antigen 7 in the yolk unless a detectable amount of the protein was present in the blood. The ovaries of polyphemus females which had been transfused with cecropia blood incorporated cecropia antigen 7 into the eggs they produced. These lines of evidence indicate that antigen 7 is secreted into the blood by some tissue other than the ovaries, and that it is subsequently drawn from the blood and deposited in the yolk. 4. The concentration of antigen 7 in the clear, liquid fraction of the yolk is four times higher than the maximum concentration attained in the blood during metamorphosis, and twenty times higher than that of the blood at the conclusion of egg formation. The protein thus appears to be transferred from blood to yolk against a concentration gradient.     

Studies on Sulfhydryl Groups during Cell Division of Sea Urchin Egg : V. Change in contractility of the thread model in relation to cell division

The contractility of the thread model prepared from the KCl-soluble proteins of the egg and in vivo factors for the contraction are investigated in Hemicentrotus, Anthocidaris, and Pseudocentrotus eggs. The contractility of the thread model induced by metal ions or cystine changes during development in the characteristic pattern of high at the metaphase and low at the monaster and the interkinetic stages. The change in contractility is paralleled by the change in the —SH content of the protein. The water-soluble fraction of the eggs has activity in causing contraction of the thread model. This activity changes during development in the same way as the contractility itself. The contraction of the thread induced by the water-soluble fractions is accompanied by a decrease in the —SH content of the thread. The activity of the water-soluble fraction in inducing the contraction is proportional to its ability to decrease the number of —SH groups. On boiling, the activity is largely destroyed. The activity is due to two components, one being non-dialyzable and the other dialyzable. Separately each component has little effect, but when mixed, the activity of the original sample is completely restored.     

Biochemistry and physiological role of methionine sulfoxide residues in proteins

The cytochrome system in eggs and embryos of the sea urchin, Hemicentrotus pulcherrimus, was investigated. Difference spectra of the mitochondrial fraction demonstrated the presence of a complete cytochrome system in unfertilized eggs. Cytochrome levels and the activities of respiratory enzymes were measured in crude extracts of eggs both before and after fertilization. Unfertilized eggs contained cytochromes aa₃, b, and c + c₁ in a ratio of 1.0:1.8:0.7. Gastrulae contained almost the same amount of cytochromes aa₃and b as unfertilized eggs. However, the amount of cytochrome c + c₁ in gastrulae was 1.5 times greater than that in unfertilized eggs. The activity of cytochrome oxidase remained unchanged during development. No cytochrome oxidase inhibitor was found in unfertilized eggs. Both antimycin A-sensitive and insensitive NADH-cytochrome c reductase activities increased during development. The activity of succinate-cytochrome c reductase increased during early development, reached a temporary plateau, and then declined at the pluteus stage. These results are discussed in relation to the increase of respiration during early development.     

Placental transfer of nutrients during gestation in the viviparous lizard, Pseudemoia spenceri

Energy, ionic, protein and lipid contents and fatty acid profiles for the major lipid classes of freshly ovulated eggs and neonates of the viviparous lizard, Pseudemoia spenceri, were measured. Litter size is 1.7 ± 0.1, with larger females producing larger neonates. Placentotrophy results in approximately 23% more dry matter in the neonates than in the fresh egg. The increase in the quantity of protein and lipid during development is not significant and is reflected in the similarity of energy densities of eggs and neonates. As a percentage of dry matter, neonates have slightly lower proportions of lipid and protein than eggs because of significant uptake of ash, calcium, potassium and sodium, but not of magnesium, across the placenta. The amounts of triacylglycerol and phospholipid are not significantly different between the egg and the neonate, but neonates contain significantly more cholesterol and cholesteryl ester. The amounts of the major fatty acids, palmitic and oleic acids, recovered from the total lipids of the neonate do not differ significantly from the amounts present in the egg lipids, but the neonates contain significantly less linoleic and α-linolenic acids and more palmitoleic, stearic and arachidonic acids than the eggs. The amount of docosahexaenoic acid recovered from the lipids of the neonate is 2.6-times greater than the amount initially present in the egg. P. spenceri has a relatively larger egg and a smaller reliance on placentotrophy than other species in the same genus, all of which have a similar placental morphology. Nevertheless, the pattern of embryonic nutrition includes both obligative and facultative placentotrophy. All the major components of yolk of oviparous species are present in eggs of P. spenceri, but most are augmented during development by placental transfer. Accepted: 8 April 1999     

Respiratory metabolism and thiabendazole susceptibility in developing eggs of Haemonchus contortus

Weston K. M., O'Brien R. W. and Prichard R. K. 1984. Respiratory metabolism and thiabendazole susceptibility in developing eggs of Haemonchus contortus. International Journal for Parasitology14: 159–164. The respiratory metabolism of and uptake of thiabendazole (TBZ) by unembryonated (8–16 cells) and embryonated eggs of Haemonchus contortus have been compared. Lipid, which forms the greatest energy reserve in the eggs, decreases during embryonation and seems to be the sole source of respiratory energy. Trehalose increases to the same extent as glycogen decreases during this development. Isocitrate dehydrogenase (NADP⁺) and lactate dehydrogenase were not detected in the unembryonated eggs, but were present after embryonation. In addition, the activities of citrate synthase and malate dehydrogenase significantly increased during embryonation. Respiratory enzymes involving cytochrome c oxidation and reduction were detected in eggs at both stages of development. However, in line with other results indicating an increased capacity for and utilization of aerobic metabolism, the rate of oxygen uptake more than tripled during development of the eggs. Although both unembryonated and embryonated eggs took up palmitate, its metabolism to CO₂ only occurred in the embryonated eggs.The unembryonated eggs, exposed to TBZ for 4 h, concentrated it 5.9 times and the embryonated eggs 2.1 times, which are in proportion to their respective lipid contents. Uptake of TBZ was dependent on the concentration in the incubation medium and appears to be a passive process.The studies indicate that the embryonated eggs have a greater capacity for, and do utilize aerobic metabolism to a greater extent than do unembryonated eggs. The reduced susceptibility of embryonated eggs to TBZ could be associated with this metabolic difference and/or with their reduced uptake of TBZ.     

Lipid metabolism during sequential gonotrophic cycles in large and small female Aedes aegypti

The lipid metabolism was investigated during six gonotrophic cycles of Aedes aegypti. Females of constant body size were analyzed for their total lipid content: large females with a body size of 41.06 (wing length cubed) and small females with 15.63. Their lipid contents at eclosion were compared to lipid values after two days of sugar-feeding, shortly before a blood meal, after oviposition, of their total egg batches, and again before the next blood meal, with intermittent access to sugar for two days for six gonotrophic cycles.Large females transferred most of their pre-blood meal lipid into the ovaries. Their low lipid content after oviposition was restored by synthesis from intermittent sugar meals. After the third gonotrophic cycle, they withheld more and more of the resynthesized lipid in their fat body, thus gradually reducing their fecundity. Since blood consumption was not altered significantly during these six cycles, age-related reduction of fecundity was clearly caused by limitations of yolk lipid.Small females transferred a considerably smaller, but constant segment of sugar-derived lipids to the ovaries. In both size classes, lipid content per oocyte was constant throughout all cycles with 9 mcal/oocyte in large and 7 mcal/oocyte in small females. Total fecundity reached 450 eggs in large and 280 eggs in small females. Large females that were maintained on water without sucrose took large blood meals from which part of the yolk lipid was synthesized. Extrapolations suggest that only one or two additional gonotrophic cycles would be possible without additional carbohydrate sources, despite lipogenesis from blood protein.     

Egg composition and reproductive investment in aphidophagous ladybird beetles (Coccinellidae: Coccinellini): egg development and interspecific variation

Abstract Most studies of insect reproductive allocation concentrate on propagule size and number and very few consider egg composition, which is likely to be equally important. In the present study, data are provided on changes in egg lipid, glycogen, free carbohydrate and protein during embryonic development of the aphidophagous ladybird Adalia bipunctata (L.) and the compositions of A. bipunctata, Adalia decempunctata and Anisosticta novemdecimpunctata eggs are compared. In A. bipunctata, egg mass, lipid and glycogen decline strongly during development and egg protein declines more weakly. Free carbohydrate declines early in egg development and increases at egg hatching. Lipid is energetically the most important developmental fuel, although approximately half of the initial egg lipid remains in the neonate larva. Across the three species, energy per unit egg mass is lowest in the least specialized species, A. bipunctata, which also has the largest eggs, and is highest in the most specialized, An. novemdecimpunctata, which has the smallest eggs. Two possible explanations for the observed pattern are discussed: (i) species laying smaller eggs may incur higher developmental costs per unit mass than species laying larger eggs and (ii) more specialized species, which reproduce at lower aphid densities, may provision neonate larvae better to facilitate location and capture of aphids.     

Structure and function of the hydropyle of the egg of the bug, Sphaerodema molestum

Changes in the wet weight, dry weight, and volume of the egg of Sphaerodema molestum during embryonic development have been studied. Also, experiments have been carried out to ascertain the route of entry of water from the environment into the egg.During development the eggs considerably increase their volume and wet weight while their dry weight progressively decreases. When the eggs of S. molestum are incubated in dye solutions, the latter penetrate through the chorionic hydropyle and reach the outer surface of the serosal hydropyle. This indicates that water enters in significant quantity through the chorionic and serosal hydropyles. The behaviour of 48-hr-old experimental eggs of S. molestum, in which the entry of water is blocked, further confirms that the intake of water is effected only through the hydropyles. The significance of the uptake of water in the eggs is discussed in relation to protein metabolism during embryogenesis.     

Maternal messenger RNA and histone synthesis in embryos of the surf clam Spisula solidissima.

Messenger RNA has been isolated from the postribosomal supernatant of Spisula solidissima eggs. This mRNA directs the synthesis of several proteins when added to the ascites or wheat germ cell free system. No histone except F1 is coded for by Spisula egg mRNA, in contrast to what has been reported previously for sea urchin egg mRNA. In sea urchin eggs histone mRNA is among the abundant species of maternal mRNA.Histones have been prepared from Spisula embryos at different development stages and histone synthesis followed by incubation with (¹⁴C)lysine. The analysis by electrophoresis on acrylamide gels indicates that the pattern of synthesis of histones changes during development and that a new histone F1 fraction is actively synthesized from the 32–64 cells stage. In earlier embryos a different F1 histone is synthesized and the mRNA for this protein may be the only histone mRNA present in eggs.     

Studies in the biochemistry of cirripede eggs. IV. The free Amino-acid pool in the eggs of Balanus balanoides (L.) and B. balanus (L.) during development

Changes in the ‘free’ amino acids, betaine, and trimethylamine oxide during the development of the eggs of Balanus balanoides (L.) and B. balanus (L.) have been determined; the results are given in terms of μM/g dry wt, μM/g water, and μM/10⁶ eggs. The amino acids are derived from the yolk proteins the net composition of which is known. Free amino acids are present in considerable quantity, as is commonly the case with crustacean tissue. Changes in the individual amino acids are discussed. B. balanus eggs contain large, and relatively constant, amounts of sarcosine; its function is unknown but large quantities are present in the more highly evolved cirripedes so far examined. A possible relation between betaine glycine, and sarcosine relative to choline metabolism is considered. Large amounts of taurine are present. There is a striking increase in β-alanine in the late stages of development; in B. balanoides it comes to be the most, and in B. balanus the third most common amino acid; its possible involvement in purine metabolism is considered. The relation between the amounts of the various entities in the eggs and in the bodies of the adult are examined.     

Storage and mobilisation of nutriment for uterine milk synthesis by Glossina morsitans

Nitrogen content of eggs and larvae of Glossina morsitans was a constant proportion of dry weight and equivalent to ca. 55% protein assuming tsetse proteins contain 16% nitrogen. The larval gut content (uterine milk) contained 40% protein. Fatty acid composition of lipids in the milk and in the larval body was similar, with Palmitic (35–38%), Palmitoleic (31–35%) and Oleic acid (23–25%) predominating. Results support the hypothesis that uterine milk contains both protein and lipid and that its composition is relatively constant throughout the period of its synthesis and secretion.Patterns of incorporation of radioactivity by fertilized adult females from injected [¹⁴C]-leucine changed throughout a pregnancy cycle. High levels of incorporation into lipid (22–30%) during early pregnancy fell to around 10% during late pregnancy. Over the same period low levels of incorporation into protein (5%) increased to 15%. Results support the hypothesis that uterine milk is synthesized from a lipid store laid down in early pregnancy coupled with protein derived largely from blood meals ingested later. Such a system would not require the insect to store proteins for larval growth and is economical in terms of energy expenditure.